1/*
2 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24#ifndef SHARE_GC_Z_ZMARKSTACKENTRY_HPP
25#define SHARE_GC_Z_ZMARKSTACKENTRY_HPP
26
27#include "gc/z/zBitField.hpp"
28#include "memory/allocation.hpp"
29
30//
31// Mark stack entry layout
32// -----------------------
33//
34// Object entry
35// ------------
36//
37// 6
38// 3 2 1 0
39// +---------------------------------------------------------------------+-+-+
40// |11111111 11111111 11111111 11111111 11111111 11111111 11111111 111111|1|1|
41// +---------------------------------------------------------------------+-+-+
42// | | |
43// | 1-1 Partial Array Flag (1-bit) * |
44// | |
45// | 0-0 Final Flag (1-bit) *
46// |
47// * 63-2 Object Address (62-bits)
48//
49//
50// Partial array entry
51// -------------------
52//
53// 6 3 3
54// 3 2 1 2 1 0
55// +------------------------------------+---------------------------------+-+-+
56// |11111111 11111111 11111111 11111111 |11111111 11111111 11111111 111111|1|1|
57// +------------------------------------+---------------------------------+-+-+
58// | | | |
59// | | 1-1 Partial Array Flag (1-bit) * |
60// | | |
61// | | 0-0 Final Flag (1-bit) *
62// | |
63// | * 31-2 Partial Array Length (30-bits)
64// |
65// * 63-32 Partial Array Address Offset (32-bits)
66//
67
68class ZMarkStackEntry {
69private:
70 typedef ZBitField<uint64_t, bool, 0, 1> field_finalizable;
71 typedef ZBitField<uint64_t, bool, 1, 1> field_partial_array;
72 typedef ZBitField<uint64_t, uintptr_t, 2, 62> field_object_address;
73 typedef ZBitField<uint64_t, size_t, 2, 30> field_partial_array_length;
74 typedef ZBitField<uint64_t, size_t, 32, 32> field_partial_array_offset;
75
76 uint64_t _entry;
77
78public:
79 ZMarkStackEntry() {
80 // This constructor is intentionally left empty and does not initialize
81 // _entry to allow it to be optimized out when instantiating ZMarkStack,
82 // which has a long array of ZMarkStackEntry elements, but doesn't care
83 // what _entry is initialized to.
84 }
85
86 ZMarkStackEntry(uintptr_t object_address, bool finalizable) :
87 _entry(field_object_address::encode(object_address) |
88 field_partial_array::encode(false) |
89 field_finalizable::encode(finalizable)) {}
90
91 ZMarkStackEntry(size_t partial_array_offset, size_t partial_array_length, bool finalizable) :
92 _entry(field_partial_array_offset::encode(partial_array_offset) |
93 field_partial_array_length::encode(partial_array_length) |
94 field_partial_array::encode(true) |
95 field_finalizable::encode(finalizable)) {}
96
97 bool finalizable() const {
98 return field_finalizable::decode(_entry);
99 }
100
101 bool partial_array() const {
102 return field_partial_array::decode(_entry);
103 }
104
105 size_t partial_array_offset() const {
106 return field_partial_array_offset::decode(_entry);
107 }
108
109 size_t partial_array_length() const {
110 return field_partial_array_length::decode(_entry);
111 }
112
113 uintptr_t object_address() const {
114 return field_object_address::decode(_entry);
115 }
116};
117
118#endif // SHARE_GC_Z_ZMARKSTACKENTRY_HPP
119